Patent Application
20060282002
The present invention generally relates to respiratory measurements, and more particularly to the construction of a respiratory testing system that can determine respiratory flow data and provide breathing exercise functions.
Spirometry tests are conventionally conducted in the prevention, diagnosis, observation and therapy of pulmonary diseases such as asthma, bronchitis, mucoviscidosis, etc. During a spirometry test, a patient induces an inspiratory or expiratory gas flow through a gas flow tube. A flow measurement mechanism measures the gas flow rate, which then may be shown on a display screen connected to the measurement mechanism.
Various types of flow measurement mechanism are implemented in existing spirometer systems. In one traditional spirometer system, a rotating fan is installed at an end of the gas flow tube. The inspiratory or expiratory gas flow induced by a user or patient through the gas flow tube causes the fan to rotate. The respiratory flow rate is inferred by counting the number of revolutions per time unit of the fan.
Another spirometer system known in the prior art uses pressure signals provided by a pressure sensor inside the gas flow tube to determine respiratory flow data. U.S. Pat. Nos. 5,111,827; 5,816,246; 6,019,731; and 6,322,519, the disclosures of which are incorporated herein by reference, describe exemplary constructions of a spirometer system based on a pressure sensor implemented as a flow measurement mechanism. The respiratory gas flow created along the gas flow tube modifies its inner pressure, which is sensed by the pressure sensor that issues an analog signal being converted into a digital form before it is inputted to a processor unit. Respiratory flow data then are computed within the processor unit, and displayed on a monitor screen.
A study of existing products available on the market reveals that improvements can be brought to the spirometer system of the prior art. For example, the spirometer functions are conventionally limited to the provision of respiratory flow data, and fail to provide useful evaluation and testing of the respiratory functions. Furthermore, the conventional construction based on a pressure sensor measurement usually puts the pressure sensor in direct contact with the respiratory gas flow induced by the user, which can result in a contamination of the sensor part by dirt or germs conveyed along with the respiratory gas flow. An air-permeable filter may be used to remedy this problem, but it adversely increases the manufacturing cost.
Therefore, there is presently a need for a spirometer system that can overcome the foregoing technical problems, and further can be manufactured with an economical cost.
In one embodiment, a respiratory testing system comprises a fluid chamber enclosing a fluid medium, and a processing circuit configured to determine respiratory flow data from a pressure variation of the fluid medium being generated in response to the application of a respiratory gas flow.
In some embodiments, the fluid medium includes air. In some embodiments, the fluid chamber includes a flexible membrane deflectable by the application of a respiratory gas flow. In some embodiments, one side of the flexible membrane is in contact with the fluid medium. In some embodiments, the processing circuit is configured to compute respiratory flow data according to a proportional relation between a pressure of the fluid medium and a respiratory flow rate.
In some variations, the respiratory testing system includes a breathing exercise unit. In some embodiments, the breathing exercise unit is operable to execute a software program configured to respond to an input of respiratory flow data.
This application also describes a method of evaluating a respiratory flow through a testing system. In some embodiments, the method comprises enclosing a fluid medium inside the testing system, sensing a pressure variation of the fluid medium in response to a respiratory gas flow applied against the fluid medium, and determining a respiratory flow rate according to a pressure variation of the fluid medium.
In some embodiments, determining a respiratory flow rate according to a pressure variation of the fluid medium includes computing a proportional relation between the pressure of the fluid medium and the respiratory flow rate. In other embodiments, the method further comprises executing a breathing exercise program configured to respond to an input of respiratory airflow data.
The foregoing is a summary and shall not be construed to limit the scope of the claims. The operations and structures disclosed herein may be implemented in a number of ways, and such changes and modifications may be made without departing from this invention and its broader aspects. Other aspects, inventive features, and advantages of the invention, as defined solely by the claims, are described in the non-limiting detailed description set forth below.
This application describes a respiratory testing system that can determine respiratory flow data and test pulmonary functions by simulating respiratory exercises.
The control body 104 encloses an electric processing circuit of the respiratory testing system. On the control body 104 are arranged a display screen 110 implementing a user graphic interface, and functional buttons 112 through which the user can control the operation of the system 100. In an embodiment, the display screen 110 may be a touch panel screen, and functional buttons 112 may include an on/off-switch button to power on the system, a reset button to reinitialize the system, and any control buttons or key pads configured to command functions provided in the system. Though the embodiment of
Referring to
In conjunction with
F=Σm·dV/dt; (1)
wherein F is the equilibrium force, m is the punctual mass of one particle transported by the gas flow 122, V is a particle velocity, and dV/dt is the time derivation of particle velocity V; and
F=P·A+Fmembrane=P·A+k·ds; (2)
wherein P is the pressure inside the air chamber 118, A is a transversal section area of the air chamber 118, Fmembrane is the reaction force produced by the membrane 120, k is the elasticity coefficient of the membrane 120, and ds is the amount of deflection of the membrane 120.
Since the constant k is substantially small (very close to 0), the term (k·ds) can be neglected and the relation (2) can be simplified to the following:
F=P·A; (2′)
On the other hand, a gas flow rate Q through the gas flow tube 102 can be expressed by the following relation:
Q=Atube·∫dV/dt·dt; (3)
wherein Q is a gas flow rate, and Atube is a transversal section area of the gas flow tube 102.
Combining the relations (1), (2′) and (3) results in the following relation in which the airflow rate Q is proportional to the pressure inside the air chamber:
Q=C·P; (4)
wherein C is a constant to be determined according to constant parameters such as the section area of the tube and the section area of the air chamber.
The equation (4) establishes a relation between a gas flow through the tube 102 and the pressure within the air chamber 118. This relation can be used to compute respiratory flow data. Additionally, depending on the pressure P inside the air chamber 118, the differences between a user's inspiratory and expiratory gas flow can be determined and trained.
A micro-controller 136 receives a digital signal reflecting the pressure inside the air chamber 118, and computes respiratory flow data such as a peak flow rate, a mean flow rate, forced expiratory volumes in successive breaths, or the like. The respiratory flow data can be shown on the display screen 110 in diverse graphic forms such as histograms, time evolution curves, numerical values or the like. In addition, the computed respiratory flow data may be further processed through a software program for additional evaluation and/or testing purposes.
Referring again to
The respiratory testing system according to this invention can be embodied in any forms. In a portable form, the respiratory testing system can be implemented in a hand-held appliance that can be conveniently manipulated by a user. Alternatively, the respiratory testing system can be integrated in a health testing station installed in a health or medical center.
Furthermore, many variations of the respiratory testing system can be implemented without departing from the inventive features described herein. For example, a mechanical assembly of movable parts (such as a sliding piston assembly) may substitute for the flexible membrane to cause a pressure variation inside the fluid chamber in response to the application of a respiratory flow.
In other variations, the fluid chamber may contain fluid elements other than air chosen with respect to their density so as to provide a pressure variation that adequately reflects the respiratory flow rate.
Realizations in accordance with the present invention therefore have been described in the context of particular embodiments. These embodiments are meant to be illustrative and not limiting. Many variations, modifications, additions, and improvements are possible. Accordingly, plural instances may be provided for components described herein as a single instance. Structures and functionality presented as discrete components in the exemplary configurations may be implemented as a combined structure or component. These and other variations, modifications, additions, and improvements may fall within the scope of the invention as defined in the claims that follow.
